The invention relates to a spray head comprising a holder body, at least one nozzle and a cover which in a protective position is arranged in front of said nozzle when the spray head is in an inactive mode, the spray head comprising means for providing a displacement of the cover from the protective position to a free position in which the cover keeps clear of the nozzle so that it can spray extinguishing medium when the spray head is in an active mode, the holder body comprising an inlet for incoming extinguishing medium.
Such spray heads are known for example from U.S. Pat. No. 4,014,388 and U.S. Pat. No. 4,880,063. The cover serves to provide an aesthetically appealing sprinkler of a type which in an inactive mode is concealed in a ceiling, for example. In such concealed sprinklers, the cover mainly serves to keep a deflect plate in a retracted position for aesthetic reasons.
In these known sprinklers, the cover falls downwards when the material holding the cover in position melts as it is exposed to heat. Once the cover falls, the heat-activated release means of the sprinkler immediately comes into contact with heat, releasing the sprinkler.
In certain surroundings, the spray heads are exposed to dust, deposits and other material that can prevent the supply of extinguishing medium in a fire by clogging the spray head nozzles. Spray heads and sprinklers are installed in order that they operate, when required, up to several years after installation and, consequently, they are naturally exposed to dirt in certain surroundings. A cover in the form of a plate (cf. U.S. Pat. No. 4,014,388 and U.S. Pat. No. 4,880,063, for example) installed in front of the nozzles mainly provides mechanical protection against impacts. Some protection against dirt may be provided, but these known sprinklers are mounted in surroundings where dirt is no problem. In certain surroundings, the amount of dirt and impurities is so high that no spray heads at all have been mounted, the assumption being that they would not operate reliably. This is the case although spray heads are most desirable in some of these applications. As examples may be mentioned open rail cars transporting expensive equipment that may catch fire, for example vehicles. Other applications include painters"" workshops and steel plants.
Mechanical loads can also make the nozzles of a spray head inoperative. Such mechanical loads may be created by impacts caused by trucks, lorries etc. in industrial halls, garages and on car decks onboard ferries.
The object and idea of the invention is to provide a spray head without said drawbacks and which, therefore, can be used in difficult, typically dirty, surroundings and which has a simple structure. The structure of the sprinkler is typically such that nozzles and other components are simultaneously protected from dirt, dust, deposits and other material which may prevent the spray head from supplying extinguishing medium.
For the above purposes, the present invention provides a spray head comprising a holder body, at least one nozzle and a cover which in a protective position is arranged in front of said nozzle when the spray head is in an inactive mode, the spray head comprising means for providing a displacement of the cover from the protective position to a free position in which the cover keeps clear of the nozzle so that it can spray extinguishing medium when the spray head is in an active mode, the holder body comprising an inlet for incoming extinguishing medium, wherein the means for providing the displacement of the cover comprises a device which is displaceable with respect to the spray heat and which is arranged by means of fluid pressure to exert a force on a locking device in the cover to make the locking device open and consequently displace the cover to said free position.
In a structurally simple embodiment of the invention, the cover is arranged to place the spray head in the active mode during the displacement.
The displaceable device preferably has a projection area which is arranged to exert the force on the locking device under fluid pressure in a pressure chamber.
The displaceable device preferably comprises a sleeve-like part which together with the holder body defines the pressure chamber, the sleeve-like part comprising the projection area in the area of the pressure chamber. Such a structure is simple and operatively reliable.
The pressure chamber can be in fluid communication with the inlet via a passage when the spray head is in the inactive mode. This being the case, an extinguishing medium pressure in the inlet provides said force against the locking device. This provides an extremely simple way for the spray head to shift to the active mode. Alternatively, according to an extremely advantageous embodiment of the invention, the pressure chamber is in connection with a control line via a passage, so that a fluid pressure in the control line is arranged to provide said force against the locking device. This embodiment is particularly suitable for so-called wet pipe systems in which the pipes are filled with pressurized extinguishing medium, and an extinguishing medium pressure acts in the inlet to the spray head without this pressure as such, i.e. without the pressure in the control line, being able to make the spray heat to shift to the active mode in which it sprays extinguishing medium.
When a sleeve-like part is used, it is preferably composed of a cylindrical part comprising a first cylindrical inner surface and a second cylindrical inner surface in the area of the pressure chamber, the first cylindrical inner surface having a larger diameter than the second cylindrical inner surface so that a shoulder forms between said cylindrical inner surfaces, the shoulder defining said projection area as a ring area. Such a cylindrical part is easy to make and easy to attach to the holder body. Furthermore, in this case the sleeve-like part is preferably sealed against the holder part by a first ring seal positioned in the first cylindrical inner surface and a second ring seal positioned in the second cylindrical inner surface in such a manner that the fluid supplied to the pressure chamber cannot flow out of the pressure chamber.
When a sleeve-like part is used, it preferably comprises a third cylindrical inner surface arranged to bear tightly against a third ring seal when the sprinkler is displaced to the active mode. This provides extra sealing against leakage; both the first and third ring seals seal against leakage.
The cover is preferably fluid-tight and hermetically arranged against the spray head by means of a seal which is preferably composed of the third ring seal. This provides the spray head with effective protection against dirt. The cover preferably comprises a cylindrical groove for the third ring seal, which groove and ring seal hold the cover in place in said protective position.
The preferred embodiments of the invention are disclosed in the attached claims 2 to 26.
One of the major advantages of the spray head is that it can be used in applications in which spray heads have not been considered to operate reliably up to now, and have therefore never been installed. In such applications the spray head of the invention is able to operate without problems. The shift of the spray head from the inactive to active mode can be achieved manually or by means of different detection systems very rapidly in different ways by means of fluid pressure. The fluid pressure can be produced for example manually by starting a pump which supplies fluid to the spray head or manually by opening a valve for supplying fluid to the spray head. The fluid pressure can be provided by means of fire detectors (e.g. smoke, heat or flame detectors) which give a signal to activate the equipment. The signal can be given to a pump which starts to supply extinguishing medium to the spray head, or the detector can be arranged to give a signal to a valve which opens so as to supply fluid (extinguishing medium, for example) to the spray head. The sensitive components of the spray head, such as nozzles, are protected against dirt, deposits and mechanical impacts. The structure of the spray head is very simple.